20.1 Defining Stored Programs

Each stored program contains a body that consists of an SQL
statement. This statement may be a compound statement made up of
several statements separated by semicolon (;)
characters. For example, the following stored procedure has a body
made up of a BEGIN ...
END block that contains a
SET
statement and a REPEAT loop that
itself contains another
SET
statement:

If you use the mysql client program to define a
stored program containing semicolon characters, a problem arises.
By default, mysql itself recognizes the
semicolon as a statement delimiter, so you must redefine the
delimiter temporarily to cause mysql to pass
the entire stored program definition to the server.

To redefine the mysql delimiter, use the
delimiter command. The following example shows
how to do this for the dorepeat() procedure
just shown. The delimiter is changed to // to
enable the entire definition to be passed to the server as a
single statement, and then restored to ; before
invoking the procedure. This enables the ;
delimiter used in the procedure body to be passed through to the
server rather than being interpreted by mysql
itself.

You can redefine the delimiter to a string other than
//, and the delimiter can consist of a single
character or multiple characters. You should avoid the use of the
backslash (“\”) character because
that is the escape character for MySQL.

The following is an example of a function that takes a parameter,
performs an operation using an SQL function, and returns the
result. In this case, it is unnecessary to use
delimiter because the function definition
contains no internal ; statement delimiters: